encased electrical device x



Nov. 28, 1,944. A. H. LAMB 2,353,796

ENCASED ELECTRICAL DEVICE Filed sept. 5, 1941 w? ga@ M7 s4 M .l 8. 32 y7 l 35 @65%,

` Patented Nov. 28, 1944 ENCASED ELEcTRIoALHDEvIoE `Anthony H. Lamb,Elizab`eth N. J., assigner to Weston Electrical Instrument Corporation,

-Newark, Nr J., a corporation of New `Jersey Application september 5,1941, seria1No.499,752 n i `1 clam. (el. zas- 23) s invention relates toencased electrical del vices, and more particularly to electricaldevices hermetically sealed within` cases which protect the devicesagainst attack `by" deleterious media l present in the atmosphere. i

Various component members of electrical dei vices are critically aiectedby dust, fumesmoisture and the like.: The movable coils `of sensitiveelectrical instruments and thev light sensitive material ofphotoel'ectric cells areespecially subject `to attack by suchatmospheric media. [Tofpro` tect these members against gradualdeterioration,

loss of eiliciency `and eventual, complete failure,

they are enclosed in some typeofmoisture proof case. However, theproblem of providing suchl cases is complicated whenthegelectricalldevice is of,` such character that a transparent `windowI Y section required jtopermit observation of the instrument lscaleplate, the transmission of `light i to the photoelectric cell, or both.

Various cements, waxes, and sealing compounds l have been employedtomake the joints Vof anfinstrument case moisture tight biitjsuch`r.`f1aterials i have not proved entirelysatisfactory asinjtime`,

they lbecomebrittle and crack or the joint sepa-4 rates under the`mechanical shocks `whichtriade#` vice encounters in normal use.` Also,the gaskets which are employed inconjunction with the glass viewingapertures deteriorate rather rapidly;

From one or both" of these causes the moisture tight characterof theinstrument case has" not been permanent; f i s Certainelectricaldeviceshave been moldeddirectly into a mass of a`transparent,"plastic mateL ria1` `but such constructions have `only a.limited field offusefulness as the temperature and pres'- surerequiredfor the molding operation `cannot be tolerated inmanyinstances. lurther,this process cannot be employed when the electrical device is `aninstrument, such as a voltmeteror an ammeter, having parts` which must`be free to moveJW c This invention contemplatesa novel manner ofconstructing an instrumentcase which is perma-` nently moistureI Aprooffand economical `to manu`` facture, and whichjdoes not require 'majorchanges` inthe design or constructionof` the cases now employed to4house electrical devices." Acase `made in accordance with thisinvention comprises a plurality of plastic sections `autogenously unitedtogether to form moisture proof `joints'. One `ormore of the casesections may be Triade` of a transpointer lying in two planes,` and amoisture proof casing enclosing the instrumentone section of the casingbeing a transparent plastic material throught; which the pointerindication may `be viewed throughout anexceedingly'large angle.

` Av still further object is the `provision ci a photoelectric `cellenclosed in a multiple section, moisture prooi case, one section ofwhichlis made of a transparent plastic to permit light to entertherethroughand strike the light sensitivesurface of the photocell.` c so n 'Ihese andother objects and advantages will be apparent from thefollowing description when taken with thel accompanying drawing. It isto be understood that the drawing is for purposes of t illustration Vandis not tobe construed as deis a photoelectric cell; i

y of prongv terminals;

parent plastic, thereby` eliminating s the needof the usual glass`viewing apertures.` s n n ,s s, An object of this invention istheprovision of lining the limits of the invention, reference being had,for this purpose; to the appended claim.

In the drawingwherein like reference charace' ters identify like |par`tsin the several figures:

Fig. 1 is` a front view of an embodiment of the invention in whichtheencased electrical device Fig. 2 is a cross sectional View of the samesubstantially asseen on the plane of line `2--2 of Fig. 1; t l

Figs. 3 and 4 are sectional views, similar to Fig. 2, illustrating otherencased photocells embodying the invention;

Fig. 5 is a side elevation, `partly in section, lof the" Fig.`.4photocell `las modiiled by the addition Fig. 6 is a front view of aphotoelectric cell and indicating instrument mounted in a single case;`

Fig. 'l is a central sectional view of the same as seen on line 1-1 ofFig. 6; Fig. 8 is a sectionalview similarto Fig. 7, `illus-` trating amodied case cover; and

Fig. 9 is a cross sectional view of alight measur- ,ing instrumentincluding apointer and-scale plate i f that may be viewed over a largeangle. s

Referring now to Figs. 1 and 2, which show an encased photocell, thecover portion I0 of the 'case'is made `preferably of a clear,transparent OFFICE N dimensions of the case sections chosen that thephotocell and associated contacts f and strike the light sensitivesurface of the photocell I I of the current-generating solid disk orbarrier layer type, Current generated by the photocell II is conductedby upper collector ring contact I2 and the lower resilient contact I3 tothe external prongs I4, as is well known in the art. A base I5, alsomade,I of a molded plastic but not necessarily transparent, isA,adapted'to be threaded into the cover I substantially as shown. Theelectrode surfaces of the photocell II and their points of electricalengagement with the terminal contacts I2, I3 are spaced from the case,and the II), I5 are so will be maintainedA in operative rrelationship bythe resilient contact I3 when said base I5 is properly seated relativeto the cover ID. Further, the

base is beveled at its outer edge to form, in conjunction, with theinner wall of the cover II), a

substantially V-shaped, circumferential groove for receiving a tackyymixture I6 comprising, in admixture with a solvent, a plastic materialof the type from which the base and cover have been formed. The mixtureis applied as a dense, t

fluid or semi-fluid mass which begins t0 harden upon application and,during the hardening process, the solvent partially `dissolves thesurfaces of the base and cover sections with which it comes intocontact. Upon evaporation of the solvent,

case comprises a cover I8 formed of a transparent.

plastic material and a base I9 also of plastic material, but notnecessarily transparent,the cover and base being autogenously united asexplained hereinabove. A vcurrent collector ring I2 establishes contactwith the front surface of the photocell disc I I and is electricallyinsulated from other portions of the disc by an insulating washer orring 20. The assembly of the photocell disc II, contact ring I2 andinsulator` 20 is retained in operative position under the pressureexerted by the raised inner section of the base I9 when the f base is inproper position. Threaded terminals casing autogenously merely byapplying a propery i`n whichthe sealing is effected by a mixture ofplastic dissolved in a suitable solvent. Such a mixture possessestheladvantage of dissolving the immediate surfaces to be united and atthe same time the interspaces which'may exist between the surfaces arelled up with the plastic as the solvent evaporates. The resulting jointi-s homogeneous and solid. L z The transparent plastic covers ofinstruments which are subject t`o excessive handling or rough usage maybe scratched at the Window surfaces as the molded plastic materials arerelatively soft. This possible objection is eliminated by theembodiment, illustrated in Fig.` 3, in which a glass disc I'I-overlies,and is molded into or cemented to, the outer end of the casing sectionIll'. The glass disc protects the transparent portion of the coverwithout affecting the moisture proo-f character of the case as a whole.'Further, the glass disc I1 may be suitably tinted to constitute a light`filter to provide a photocell having a desired spectral response, as iswell known in the art. natively, a filter effect may be achieved' byforming the case cover of a suitably tinted or colored plastic material.

' A photoelectric cell case made in two sections To provide suchpressure f" A-.lter- 2| are molded into base 20 and reinforced by thenuts 22, 23 at the inner and outer' faces, respectively, of the base.Internal electrical connections to the terminals 2| are provided by theusual soldered jumper connections or, as shown, by coiled springs 2,4seated within bores in the ends of the respective terminals 2I andestablishing pressure contacts against the inturned portion of the`contact ring I2 and against the back of photocell disc I I.

It is often desirable to mount a photocell into a common radio tubesocket to facilitate replacement, and units designed for such mountingare provided with prong connectors of the typeillustrated in Fig. 1. maybe provided with an adapter for this purpose, as shown in Fig. 5. Theadapter terminals 25, 26 of different diameters have apertured innerends that are tted over and rigidly secured to terminals 2I by nuts 21.A domed cover 2B is preferably fltted over the adapter terminals, andheld in position :by nuts 29, to improve the general appearance of thecompleted unit.

Hermetically sealed cases, made according to this invention may beadvantageously employed to house electrical instruments which requirerelative movement of various members for operation. `By way of example,such an instrument, namely an illumination meter, is shown in Figs. 6-8.It comprises a photocell II which, under the action of light, actuatesthe movable coil 30 of a permanent magnet, movable coil type instrument.The deflection of instrument pointer 3I with respect to a suitablycalibrated scale 32 is a measure of the light striking the surface ofthephotocell. Both the photocell and the instrument are housed in asingle case comprising a transparent plastic cover 33 and a plastic base34. The base 34 has a beveled edge which forms a peripheralgroove alongthe side wall .of the cover 33, this groove being lled with the plasticmixture 35 to join the base and cover, as explained hereinabove. Whensealing up a relatively large chamber, temperature changes or a slightalteration in the relative disposition of the base or cover may causethe air Within the chamber to expand or contract. Such breathing duringthe time that the plastic mixture is hardening may result in animperfect seal and, to eliminate this possibility, the base 34 isprovided with a small hole 36 which permits ready transfer of the airwhile the base and cover sections are being permanently united. Oncethis has been accomplished, the tiny hole may be sealed by applying adrop 31 of the plastic mixture.

To prevent possiblescratching of the operative section of the plasticcase cover, the cover may The photocell shown in Fig. 4

be modified, as shown in Fig. 8, to include a protecting glass plate 38over the top surface of the cover section 33'. l l f When the coversection of the instrument case is made of a transparent plasticmaterial, the I internal mechanism of the instrument may be pointerdeflection. The cover l39` and thebase the sealing section of the casngswith a milling scribed above. `The light to be measured passes throughthe transparent base` and strikes the photocell 1Il `which is connectedto `movable coil ably calibrated scale plate 43. The outer end of thepointeris bent downwardly at substantially a right angle, as shown, andthescale plate 43 has both a radial and a cylindrical surface. It willbe apparent that the calibration markings may be formed on both portionsof the plate 43, and

that theposition of the pointer relative to said *y `calibrations maythen be observed from either a vertical or horizontal position.

Portionsfof `a transparent casing member ma be rendered opaq.ueif`desired, byspraying an enamel upon the sections through which there isto be no transmission of light. The hermetically sealed casings may beopened for repair or rel cutter of conical orother appropriate `form.

`tion,as set forth in the l Having now described various embodiments ofl, my invention,v it will be apparent that other variations andmodifications are permissible without departing from the spirit andscope of the invenclaim.

I claim: l

An encased electrical devicecomprising a measuring instrument having apivotally mounted coil carrying a pointer, a scaleplate anda photocellof the disk type, such `parts of the instrument being mounted whollywithin the `confines of an integral hollow substantially concave casing,por- 15 4l of the measuring instrument. A pointer 42 ist aflixed to thecoil 4I and cooperates with a suit placement of the electrical devicesby cutting out'` tions `of said casing being transparent, said portionsbeing in the bottom wall of said casing,

said scale plate being mounted adjacent and facing one of such portionsand said photocell bel ing mounted adjacent and facing another of suchportions,` said casing being sealed by means of a cover, said coverbein-g of the same material as said casing and being autogenouslysecured to said casing by means of a mass of plastic materialofsubstantially the same chemical composition as said casing andcover,`said mass extending along the ilat contacting faces of saidcasing and' cover, said transparent portions being disposed in side byside vrelationship whereby the effort exerted upon one `side of thephotocellis readable upon the scale, from the same side ofthe photodcell.

ANTHONY H. LAMB.

